/* The MIT License

   Copyright (C) 2011 Zilong Tan (tzlloch@gmail.com)

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   "Software"), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
*/

#ifndef __ULIB_HASH_H
#define __ULIB_HASH_H

#include <stdio.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * hash_djb2 - Bernstein's Hash, useful for short strings
 * @str: string buffer
 */
	uint32_t hash_djb2(const unsigned char *str);

/**
 * hash_sdbm - SDBM Hash, another good choice for strings
 * @str: string buffer
 */
	uint32_t hash_sdbm(const unsigned char *str);

/**
 * hash_fnv32 - 32-bit FNV-1a Hash, for general purpose hashing
 * @buf: data buffer
 * @len: data size
 */
	uint32_t hash_fnv32(const unsigned char *buf, size_t len);

/**
 * hash_fnv64 - 64-bit FNV-1a Hash, for general purpose hashing
 * @buf: data buffer
 * @len: data size
 */
	uint64_t hash_fnv64(const unsigned char *buf, size_t len);

/**
 * hash_murmur32 - a 32-bit implementation of murmurhash2
 * @buf:  data buffer
 * @len:  data size
 * @seed: the seed
 */
	uint32_t hash_murmur32(const unsigned char *buf, size_t len, uint32_t seed);

/**
 * hash_murmur64 - a 64-bit implementation of murmurhash2
 * @buf:  data buffer
 * @len:  data size
 * @seed: the seed
 */
	uint64_t hash_murmur64(const unsigned char *buf, size_t len, uint64_t seed);

/**
 * hash_crapwow64 - a 64-bit implementation of crapwow hashing
 * @buf:  data buffer
 * @len:  data size
 * @seed: the seed
 * Note: only available for x86_64
 */
	uint64_t hash_crapwow64(const unsigned char *buf, uint64_t len, uint64_t seed);

/**
 * hash_crapwow32 - a 32-bit implementation of crapwow hashing
 * @buf:  data buffer
 * @len:  data size
 * @seed: the seed
 * Note: only available for x86_64
 */
	uint32_t hash_crapwow32(const unsigned char *buf, uint32_t len, uint32_t seed);

/**
 * hash_crc32 - an implementation of CRC-32
 * @buf: data buffer
 * @len: data size
 */
	uint32_t hash_crc32(const unsigned char *buf, size_t len);

/*
  --------------------------------------------------------------------
  This works on all machines.  To be useful, it requires
  -- that the key be an array of uint32_t's, and
  -- that the length be the number of uint32_t's in the key

  The function hashword() is identical to hashlittle() on little-endian
  machines, and identical to hashbig() on big-endian machines,
  except that the length has to be measured in uint32_ts rather than in
  bytes.  hashlittle() is more complicated than hashword() only because
  hashlittle() has to dance around fitting the key bytes into registers.
  --------------------------------------------------------------------
*/
	uint32_t hashword(const uint32_t * k,	/* the key, an array of uint32_t values */
			  size_t length,	/* the length of the key, in uint32_ts */
			  uint32_t initval);	/* the previous hash, or an arbitrary value */

/*
  --------------------------------------------------------------------
  hashword2() -- same as hashword(), but take two seeds and return two
  32-bit values.  pc and pb must both be nonnull, and *pc and *pb must
  both be initialized with seeds.  If you pass in (*pb)==0, the output 
  (*pc) will be the same as the return value from hashword().
  --------------------------------------------------------------------
*/
	void hashword2(const uint32_t * k,  /* the key, an array of uint32_t values */
		       size_t length,       /* the length of the key, in uint32_ts */
		       uint32_t * pc,       /* IN: seed OUT: primary hash value */
		       uint32_t * pb);      /* IN: more seed OUT: secondary hash value */

/*
  -------------------------------------------------------------------------------
  hashlittle() -- hash a variable-length key into a 32-bit value
  k       : the key (the unaligned variable-length array of bytes)
  length  : the length of the key, counting by bytes
  initval : can be any 4-byte value
  Returns a 32-bit value.  Every bit of the key affects every bit of
  the return value.  Two keys differing by one or two bits will have
  totally different hash values.

  The best hash table sizes are powers of 2.  There is no need to do
  mod a prime (mod is sooo slow!).  If you need less than 32 bits,
  use a bitmask.  For example, if you need only 10 bits, do
  h = (h & hashmask(10));
  In which case, the hash table should have hashsize(10) elements.

  If you are hashing n strings (uint8_t **)k, do it like this:
  for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);

  By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
  code any way you wish, private, educational, or commercial.  It's free.

  Use for hash table lookup, or anything where one collision in 2^^32 is
  acceptable.  Do NOT use for cryptographic purposes.
  -------------------------------------------------------------------------------
*/

	uint32_t hashlittle(const void *key, size_t length, uint32_t initval);

/*
 * hashlittle2: return 2 32-bit hash values
 *
 * This is identical to hashlittle(), except it returns two 32-bit hash
 * values instead of just one.  This is good enough for hash table
 * lookup with 2^^64 buckets, or if you want a second hash if you're not
 * happy with the first, or if you want a probably-unique 64-bit ID for
 * the key.  *pc is better mixed than *pb, so use *pc first.  If you want
 * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
 */
	void hashlittle2(const void *key,  /* the key to hash */
			 size_t length,    /* length of the key */
			 uint32_t * pc,    /* IN: primary initval, OUT: primary hash */
			 uint32_t * pb);   /* IN: secondary initval, OUT: secondary hash */

/*
 * hashbig():
 * This is the same as hashword() on big-endian machines.  It is different
 * from hashlittle() on all machines.  hashbig() takes advantage of
 * big-endian byte ordering. 
 */
	uint32_t hashbig(const void *key, size_t length, uint32_t initval);

#ifdef __cplusplus
}
#endif

#endif  /* __ULIB_HASH_H */
